1. Field of the Invention
The present invention relates to heat blowers, and particularly to a heat isolation cover for a heat blower which has a simple structure. The contact area between the heat resistance unit and the protection sleeve is reduced. The through holes and the protection sleeve will cause the contact temperature and the return heat can be reduced. Thereby cost is low and the assembly work is easy. Thus, the heat blower is a safety device.
2. Description of the Related Art
Referring to FIG. 1, the prior art heat blower 1 is illustrated. The prior art heat blower has a casing 10. An inner tube 13 is installed with the casing 10 by using an annular rib 11 or a metal ring 12. A hollow interior of the inner tube 13 has a high impedance heat resistance unit 14 for generating heat. One end of the inner tube 13 has a fan and motor set 15 having a circuit board. The fan and motor set 15 blows air to the inner tube 13 and the heat resistance unit 14 and hot air flows out from another end of the inner tube 13.
In above mentioned heat blower 1, in actuation, the heat resistance unit 14 will generate heat continuously, even it achieves to 500° C. However, the heat will transfer to the inner tube 13, but the air from the fan and motor set 15 only blows the inner tube 13 and thus the temperature from the heat source can not reduce continuously. Furthermore because the heat accumulates, the casing 10 made of plastics will increase continuously. As a result, it is possible that the casing 10 will melt.
Moreover, the high temperature of the heat blower 1 will make heat accumulate in the inner tube 13, even the power of the heat blower 1 is turned off. However, the heat residue in the heat resistance unit 14 and inner tube 13 will accumulate in the casing 10 without the blowing of the fan and motor set 15. As a result, the heat returns to the casing 10 so as to destroy the casing 10, even the heat transfers to the fan and motor set 15 to burn the circuit of the motor.
Referring to FIG. 2, in one improved structure, a protection sleeve 16 is installed at a periphery of the inner tube 13 of the heat blower 1, the inner tube 13 is assembled to the casing 10 (referring to FIG. 2). An interior surface of the protection sleeve 16 has a plurality of projections 17 resisting against an inner periphery of the inner tube 13 so as to form a gap therebetween. Then the protection sleeve 16 encloses the inner tube 13 and is positioned at a predetermined position of the casing 10. By the protection sleeve 16 and the fan and motor set 15, the heat of the heat blower 1 can be reduced effectively. The contact points between the protection sleeve 16 and the inner tube 13 will make the heat from the casing 10 reduce so as to prevent the heat blower from high temperature.
However, from above mentioned structure, the heat from the inner tube 13 to the casing 10 will generate high temperature as the heat blower is used for a long time. Furthermore when the heat blower 1 is not used, the residual heat will make the temperature increase. Thus there is a necessity for improving the prior art heat blower.